How to increase tables space, resizing, backups and when I you do?

Hello guys,

I am new comer in Basis. I want the information regarding some DB maintenance task. I am getting confusion in table space management. I don't know how to increase the table spaces, observe and manage the table spaces in SAP. How to resize the table space. i have some backup scheduling task and I am able to take that backup through DB13 T-code. I scared about that i this backup is useful for restore or not?

So please assist me.

Waiting for reply.